Cable television systems are well known in the art. Through such systems, a recipient's television receiver may be connected to a cable that connects to the cable company's transmitter. A plurality of television signals are broadcast in the radio frequency range through the cable.
Attempts have been made to send additional messages through such cable systems. For instance, in some prior art systems, a written message appears on the screen of the recipient's receiver. This message may either contain all of the pertinent information that the cable company intends the recipient to receive, or it will instruct the viewer to turn to a specific channel. The intended information will then be viewable on that channel.
Such a system has certain obvious drawbacks. Most important, the receiver must be turned on, or the recipient will not be aware that the cable company has transmitted a message.
To overcome this drawback, the applicant herein provided a communications apparatus suitable for use with a cable television system that would operate even when the recipient's television receiver is deactivated, as more specifically set forth in the applicant's U.S. Pat. No. 4,575,750. The communications system of that patent included a transmission unit which provided at least one recorded audio signal message. The transmission unit would convert the message into a radio frequency signal broadcast through the cable television system without interfering with any signals ordinarily broadcast therethrough. A receiver is provided at each cable television subscriber's location for receiving the radio frequency signal from the transmitter and for converting that signal into an audible signal. The receiver included a transducer which was separate from the transducer elements ordinarily connected to the cable television system, to permit an audible signal to be produced without requiring that the television set be turned on.
While the communications system of U.S. Pat. No. 4,575,750 has worked well for its intended purpose, it would only send one specific signal as a result of a single input at the cable head end. Thus, the prior art communications system could not receive input from multiple sources and process that information to produce an appropriate alarm signal.
The capability of receiving alarm activation inputs from several sources permits the transmission of a wide variety of warning messages. For example, severe weather warnings could be issued to subscribers in a threatened area. Civil defense messages or environmental health warnings could also be received and delivered through a single system. Manual triggering of recorded voice messages could be transmitted through a telephone input.
Use of multiple sources of input leads to several other features not present in the prior art. First, a priority structure is desirable in the event of simultaneous activation of two or more inputs. Second, the multiple input processor should have self-monitoring ability as well as the capability of issuing reports of its functioning. In addition, communications via a standard modem permits reporting through a telephone interface as well as control of the processor via a telephone interface.